Fix coordination for using R4 in Thumb1 as a scratch for SP restore.
The logic for reserving R4 for use as a scratch needs to match that for
actually using it. Also, it's not necessary for immediate <=508, so adjust
the value checked.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132934 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/ARMFrameLowering.cpp b/lib/Target/ARM/ARMFrameLowering.cpp
index e2e95d4..516e34a 100644
--- a/lib/Target/ARM/ARMFrameLowering.cpp
+++ b/lib/Target/ARM/ARMFrameLowering.cpp
@@ -841,9 +841,14 @@
if (AFI->getVarArgsRegSaveSize() > 0)
MF.getRegInfo().setPhysRegUsed(ARM::LR);
- // Spill R4 if Thumb1 epilogue has to restore SP from FP since
+ // Spill R4 if Thumb1 epilogue has to restore SP from FP. We don't know
+ // for sure what the stack size will be, but for this, an estimate is good
+ // enough. If there anything changes it, it'll be a spill, which implies
+ // we've used all the registers and so R4 is already used, so not marking
+ // it here will be OK.
// FIXME: It will be better just to find spare register here.
- if (MFI->hasVarSizedObjects())
+ unsigned StackSize = estimateStackSize(MF);
+ if (MFI->hasVarSizedObjects() || StackSize > 508)
MF.getRegInfo().setPhysRegUsed(ARM::R4);
}